My experience with CA DMV INF 70 requests for info before the late 80's has been futile. Having worked in the IT/database world for 40+ years, since the MS DOS 2.1 and DBase II days and multiple database upgrades, with the DMV having gone through several OS/database/software upgrades over the decades, sometimes a decision is made "we can't migrate that old data, we've got it on microfiche, right? And who's going to want to look at that useless old data anyway!"
And even though the form says they will look at microfilm, I'm not so sure those state workers will that for $20. Or what tools they have available to them. Searching microfilm is not fun, and unless they've scanned the microfilm into a searchable database or document, almost impossible.
But maybe worth a shot. Just remember it's California you're dealing with.